This invention relates to the manufacturing process for automotive vehicle bodies including those for passenger cars, trucks, and sport utility vehicles.
Automobile manufacturers commonly produce automotive vehicle bodies that are primarily comprised of formed metal body panels. These panels are typically formed by cutting and stamping initially flat sheets of metal in an elaborate multi-stage die stamping process. Such formed metal panels are subsequently fastened together to form subassemblies and final assemblies which define the vehicle architecture. This architecture serves as the partial exterior of the vehicle as well as its primary structure in many cases. Fastening methods for the metal panels and subassemblies include spot welding, laser welding, screwing, riveting, bolting, clinching, and structural adhesives.
Current automotive body assemblies are therefore primarily weldments of smaller pieces of formed sheet metal. In order to accommodate the welding process, flanges for weld placement are often created along the edges of the formed sheet metal. These flanges have the effect of increasing the amount of material in the weld regions, adding mass, and hence weight, to the vehicle body. In addition, the welds are the primary load path between mating components and constitute a structural discontinuity between the parent parts. Should these welds fail or be poorly executed, the structural integrity of the assembly can be compromised.
Some formed metal panels, for example the front fenders and hood, are considered to be non-structural and of little value for crashworthiness. They exist primarily for general closure, vehicle aerodynamics, and styling purposes.
Several manufacturers have substituted aluminum or plastic panels for some of the steel body components. Examples include the hood, fenders and deck lid. One plastic material commonly employed is sheet molding compound. These components must be attached to the remaining structure using a variety of methods including adhesives and fasteners.
Vehicle bodies manufactured by existing processes are comprised of a significant number of individual parts. Spot welding, the predominant method of attaching these parts together, is an expensive process requiring extensive support facilities.
Thermal spray is a material deposition technique in which a material initially in solid form is melted or softened and then propelled onto the surface of a substrate material to form an exterior coating. Once the molten metal has solidified, the substrate material benefits from the presence of a superior material on its exterior surface. In this scenario, the substrate surfaces provide location for the thermal spray material. Prior to melting, the metal can exist in wire form, powder form, or other forms suitable to the application.
Thermal spray processes can be classified by the two methods that are used to generate heat, namely electrical heating and chemical combustion. Electrical heating includes plasma spraying and wire arc spraying. Chemical combustion includes detonation/explosive flame spraying, wire/rod flame spraying, and powder flame spraying.
Marine applications include the use of thermally sprayed coating materials for protection from aquatic environment. Computer industry usage of thermal spray includes coating computer components with aluminum in order to suppress electromagnetic interference. Automotive applications include the coating of internal combustion engine cylinder bores in order to achieve desirable surface qualities.
Accordingly, several objects and advantages of the present invention are:
(a) to enable the production of a structurally superior and lighter weight vehicle body structure through the usage of an optimized formed substrate in conjunction with variable exterior thermal spray material thicknessesxe2x80x94in other words to apply customizeable spray material thicknesses as needed to a well designed vehicle body core shape;
(b) to allow the design and production of a lighter weight automotive vehicle which obtains greater fuel economy and therefore saves energy;
(c) to reduce or eliminate sheet metal stamping in the manufacture of automotive vehicle bodies;
(d) to reduce or eliminate welding and the manufacturing challenges associated with it for automotive vehicle bodies;
(e) to reduce the amount of material required in vehicle bodies by reducing or eliminating the flanges that welding requires in assemblies and subassemblies;
(f) to produce a more continuous vehicle body design by enabling the creation of larger vehicle body components;
(g) to allow for a reduction in the number of separate parts required in a vehicle bodyxe2x80x94in other words to reduce the part count in a vehicle body;
(h) to enable the creation of a closed sandwich composite structure fabricated by thermal spraying on all sides of a substrate core material;
(i) to enable the creation of an open composite structure by thermal spraying on only some sides of a substrate core material;
(j) to facilitate the fabrication of rapid prototype vehicle structures by the application of thermal spray to hand-shaped or machined substrate cores;
(k) to facilitate the fabrication of production vehicle structures by the application of thermal spray to molded substrate cores.
Further objects and advantages are the ability to design and manufacture a more rigid body structure which provides for increased vehicle occupant safety, and which promotes improved vehicle dynamics including acceleration, braking and handling. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.